Su Zhong, Hsi Wen, Forthomme Julien, Rossomme Séverine
Department of Radiation Oncology, University of Florida, Gainesville, FL, USA; University of Florida Health Proton Therapy Institute, Jacksonville, FL, USA.
Department of Radiation Oncology, University of Florida, Gainesville, FL, USA; University of Florida Health Proton Therapy Institute, Jacksonville, FL, USA.
Phys Med. 2020 Dec;80:243-250. doi: 10.1016/j.ejmp.2020.10.026. Epub 2020 Nov 14.
To evaluate the flat-panel detector quenching effect and clinical usability of a flat-panel based compact QA device for PBS daily constancy measurements.
MATERIALS & METHOD: The QA device, named Sphinx Compact, is composed of a 20x20 cm flat-panel imager mounted on a portable frame with removable plastic modules for constancy checks of proton energy (100 MeV, 150 MeV, 200 MeV), Spread-Out-Bragg-Peak (SOBP) profile, and machine output. The potential quenching effect of the flat-panel detector was evaluated. Daily PBS QA tests of X-ray/proton isocenter coincidence, the constancy of proton spot position and sigma as well as the energy of pristine proton beam, and the flatness of SOBP proton beam through the 'transformed' profile were performed and analyzed. Furthermore, the sensitivity of detecting energy changes of pristine proton beam was also evaluated.
The quenching effect was observed at depths near the pristine peak regions. The flat-panel measured range of the distal 80% is within 0.9 mm to the defined ranges of the delivered proton beams. X-ray/proton isocenter coincidence tests demonstrated maximum mismatch of 0.3 mm between the two isocenters. The device can detect 0.1 mm change of spot position and 0.1 MeV energy changes of pristine proton beams. The measured transformed SOBP beam profile through the wedge module rendered as flat.
Even though the flat-panel detector exhibited quenching effect at the Bragg peak region, the proton range can still be accurately measured. The device can fulfill the requirements of the daily QA tests recommended by the AAPM TG224 Report.
评估基于平板探测器的紧凑型质量保证（QA）设备对笔形束扫描（PBS）每日稳定性测量的平板探测器猝灭效应及临床可用性。
名为Sphinx Compact的QA设备由一个20×20 cm的平板成像器组成，该成像器安装在便携式框架上，带有可移除的塑料模块，用于质子能量（100 MeV、150 MeV、200 MeV）、扩展布拉格峰（SOBP）轮廓和机器输出的稳定性检查。评估了平板探测器的潜在猝灭效应。通过“变换”后的轮廓，对X射线/质子等中心重合性、质子束斑位置和标准差的稳定性以及原始质子束能量的每日PBS QA测试，以及SOBP质子束的平整度进行了测试和分析。此外，还评估了检测原始质子束能量变化的灵敏度。
在原始峰区域附近的深度处观察到猝灭效应。平板探测器在远端80%的测量范围内与所输送质子束的定义范围相差在0.9 mm以内。X射线/质子等中心重合性测试表明，两个等中心之间的最大不匹配为0.3 mm。该设备能够检测到束斑位置0.1 mm的变化以及原始质子束0.1 MeV的能量变化。通过楔形模块测量的变换后的SOBP束轮廓显示为平坦。
尽管平板探测器在布拉格峰区域表现出猝灭效应，但质子射程仍可被准确测量。该设备能够满足美国医学物理师协会（AAPM）TG224报告推荐的每日QA测试要求。
